The objective of this research was to measure the absorption and reduced scattering coefficients (μ_a and μ_s', respectively) of apples via a spatially-resolved hyperspectral imaging technique and relate them to fruit firmness and soluble solids content (SSC). Spatially-resolved hyperspectral images were acquired from 600 'Golden Delicious' apples, and values for μ_a and μ_s' were determined using an inverse algorithm to fit the diffusion theory model to the spectral scattering profiles over 500-1000 nm. There were two predominant peaks in the absorption spectra around 675 nm and 970 nm due to the presence of chlorophyll and water in the fruit, respectively. Spectra of μ_s' decreased monotonically with the increasing wavelength. Both μ_a and μ_s' were correlated with fruit firmness, with the correlation coefficient (r) of 0.82 and 0.80, respectively. Values of μ_a were also correlated with the SSC with r = 0.70. The combined data of μ_a and μ_s' were able to predict fruit firmness with r = 0.88 and the standard error of prediction (SEP) of 5.66 N, and SSC with r = 0.82 and SEP = 0.75%. This research demonstrated the potential of using spectral absorption and scattering properties to evaluate internal quality attributes of horticultural products.

Date Published: 12 October 2007
PDF: 11 pages
Proc. SPIE 6761, Optics for Natural Resources, Agriculture, and Foods II, 67610M (12 October 2007); doi: 10.1117/12.751937

Published in SPIE Proceedings Vol. 6761:
Optics for Natural Resources, Agriculture, and Foods II
Yud-Ren Chen; George E. Meyer; Shu-I Tu, Editor(s)